Date: Tue, 10 Mar 2009 17:05:52 +0100 From: Alexej Sokolov <bsd.quest@googlemail.com> To: freebsd-hackers@freebsd.org Subject: write protection by mmap of /dev/mem doesn't work Message-ID: <671bb5fc0903100905u7484cd1dp9faefc8bc208a6a6@mail.gmail.com>
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hello,
How can I mmap some memory regions with PROT_WRITE protection flag ?
What i do:
/* Open mem device */
if ((devmem_fd = open("/dev/mem", O_RDWR)) == -1){
perror("/dev/mem");
exit (1);
}
then if I try to mmap some memory region with PROT_READ it goes Ok. But by
PROT_WRITE it doesn't work:
sp = mmap ( 0,
MCLBYTES, /* Size of remapped buffer = size of
mbuf cluster */
PROT_WRITE,
MAP_SHARED,
devmem_fd,
phys_addr /* Physical addres of packet buffer
from descriptor */
);
I get by PROT_WRITE " segmentation fault"
What is the problem here ?
And question again:
How can I do it possible to remapp the kernel memory region to user space
process through /dev/mem and give to this user process write permissions to
remmaped space ?
Thanx
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